SEARCH FOR A SPECTRAL CHANGE OF AN ULTRACOLD NEUTRON GAS IN A TRAP

In a recent measurement of the spectrum of ultracold neutrons (UCN), a s it evolves during storage in a ''neutron bottle'', we had observed a n indication of unexplained small heating of order 5 x 10(-11) eV. The effect was on the 3 sigma-level. A confirmation of such an effect mig ht have important theoretical implications. Here we report the results of a new measurement performed in an almost identical setup but with significantly poorer monochromaticity although somewhat better statist ics. It showed no measurable energy change and, therefore, did not pro vide unambiguous support for the earlier indications. (C) 1998 Publish ed by Elsevier Science B.V.